Analytical instruments are used both in laboratories and in the production or process fields for chemical and/or physical analysis, such as in quantitative analysis, for example. Quantitative analysis is a chemical and/or physical procedure for determining the quantity or amount of a material or a substance in a sample to be analysed. An analytical instrument may be what is known as a bench-top instrument, hand-held instrument or in-line instrument. In addition, analytical instruments are also used in order to determine other chemical and/or physical properties or parameters of a sample.
Examples of analytical instruments of this type are titrators, UV/VIS spectrometers, refractometers and instruments for measuring density, for determining pH, for determining redox potentials, for conductivity determination, for ion determination and/or for the determination of dissolved gases. Using such instruments, various parameters of at least one substance in a sample can be determined, examples of which are the concentration, amount, density, refractive index, pH, redox potential and/or conductivity. Analytical instruments can be fitted out for determining one or more parameters of a sample.
The functional capability of analytical instruments should be regularly tested in order to ensure that the quality and reproducibility of the measurement results is consistent. Regular testing is generally carried out by the operator, who measures one or more known samples and compares the result with an expected set value. Samples which have contents and parameters or set values which are known to the operator are known as “known” samples. Samples in which the contents, parameters or set values are unknown to the operator, but are known to the person submitting them, are “blind” samples and are used to test the validity of a measurement instrument or an analytical instrument or of the process being conducted on the instrument. In addition, analytical instruments can be serviced on site by the manufacturer or a certificated service engineer; this is very expensive for the operator and thus is mainly only carried out in areas and/or applications for which appropriate independent certification is required.
In order to carry out the testing successfully, the operator should have a great deal of experience using the analytical instrument to be tested and above all be able to guarantee that the samples to be examined are of consistent quality. The chemical and/or physical analytical methods provided as examples are very precise and react to the slightest contamination of the sample due to foreign bodies and/or old samples with erroneous readings. Measuring a contaminated and/or old sample provides a measuring result which is correct for that sample, but which deviates substantially from the expected result for the known and preferably pure sample. Testing an analytical instrument by an operator can thus be fraught with errors, and in addition can be influenced by the operator who is aware of the physical and/or chemical processes which are occurring.
Thus, there is a need for a method for independent testing and/or validation of an analytical instrument which is simple and inexpensive for the operator to carry out, and for an analytical instrument for carrying out this method. The aim of the method is, inter alia, to reduce operator-derived errors, examples of which are errors in weighing out and/or dosing errors, so that even inexperienced operators can carry out a reliable and independent test of the analytical instrument.